Mechanism for holding a tubular core

ABSTRACT

This invention relates to a mechanism for securely holding a tubular core on which a band of material such as photographic paper is to be wound. The core is held by a gripping mechanism inside a mandrel on which the core is mounted. Running through the mandrel coaxially therewith is a rotatable shaft having three rollers each mounted on a different apex of a triangular plate securely coupled to the shaft. Studs radially located within the mandrel are positioned to be engaged by the rollers so that on rotation of the shaft relative to the mandrel the studs protrude through the periphery of the mandrel to grip the core. A friction clutch between the mandrel and the shaft is provided to hold them in position after the studs have been engaged with the core.

ilnite States atent Binder 1 June 6, 1972 Appl. No.: 885,491

FOREIGN PATENTS OR APPLICATIONS 1,372,400 8/1964 France ..242/46.5 917,978 2/1963 GreatBritain ..242/46.4

Primary Examiner-George F. Mautz Assistant ExaminerGregory A. Walters Attorney-Pierce, Scheffler & Parker [57] ABSTRACT This invention relates to a mechanism for securely holding a tubular core on which a band of material such as photographic paper is to be wound. The core is held by a gripping mechanism inside a mandrel on which the core is mounted. Running through the mandrel coaxially therewith is a rotatable shaft having three rollers each mounted on a different apex of a triangular plate securely coupled to the shaft. Studs radially located within the mandrel are positioned to be engaged by the rollers so that on rotation of the shaft relative to the mandrel the studs protrude through the periphery of the mandrel to grip the core. A friction clutch between the mandrel and the shaft is provided to hold them in position after the studs have been engaged with the core.

6 Claims, 3 Drawing Figures PATENTEDJUH 6 I972 3.667. 697

SHEET 1 OF 2 Erich Binder PM s wggwx 1 adoww v MECHANISM FOR HOLDING A TUBULAR CORE The invention relates to mechanism for securely locating and holding tubular bobbins, spools or cores, particularly cores for winding and unwinding a band of photographic printing paper.

In a known locating and holding device of this kind a mandrel is fast on a drive shaft and actuating elements are formed by a coaxial camshaft which is freely rotatable inside the mandrel but locatable in certain angular positions by a locking nut. For mounting and securing as well as for releasing a core on which, for example, a band of photographic material is to be wound, the locking nut must be slackened off, the camshaft rotated and the locking nut tightened again. The operations of mounting and releasing a winding core are therefore complicated as well as time-consuming. Another defect is that for turning the camshaft and for slackening off and retightening the locking nut a special tool may be required.

In the present invention we provide a mechanism for locating and holding a tubular winding core on a mandrel carried by a drive shaft the mandrel including movable gripping means arranged to be pushed radially outwards against a resilient restoring means by one or more elements located centrally in the mandrel, in which the winding mandrel is frictionally coupled to the drive shaft and the actuating element(s) for displacing the gripping means is or are coupled to the drive shaft for rotation therewith in such manner that rotation of the mandrel relative to the drive shaft causes the actuating element(s) to force the gripping means radially outwards.

The drawbacks of the aforementioned known form of locating and holding device are substantially overcome since the winding mandrel is frictionally connected to the drive shaft, whereas the actuating elements for displacing the gripping means are fast on the drive shaft in such manner that rotation of the mandrel on the drive shaft causes said actuating elements on the drive shaft to force the gripping means radially outwards.

The invention thus has the further advantage over the aforementioned mechanism that the disposition of the actuating elements directly on the drive shaft eliminates the need for a special camshaft.

The invention will be more particularly described with reference to an embodiment shown in the drawings in which:

FIG. 1 is a part sectional side view of the proposed mechanism,

FIGS. 2a and 2b are sections taken on the line II II in FIG. 1, showing the mechanism in two different operating positlons.

Referring to FIG. 1 a baseplate 1 carries a bearing sleeve 2 in which a drive shaft 5 connected by means of a flexible coupling 8 to a motor shaft 9 is mounted in two ball races 3 and 4. A braking disc 6 and a substantially triangular flange 7 are fast on the drive shaft 5. At each corner the flange carries a roller 13 mounted on an axle pin 11. Rotatably and axially movably mounted on the drive shaft 5 on bearing bushes l6 and 17 is a winding mandrel 14 to which a cover plate 15 is attached. Likewise, attached to the winding mandrel 14 are a friction disc 18 and a flange 19. The front end of the drive shaft 5 carries a nut 25 which can be locked in any position by a fixing screw 26. lnterposed between the nut 25 and the bush 17, which is firmly connected to a friction disc 18 by the cover plate 15 and the winding mandrel 14, is a coil spring 27 which therefore operates to urge the friction disc 18 into contact with the brake disc 6 to establish a friction clutch. A winding core 29 mounted on the mandrel is also shown in the drawing in dot-dash lines. For guiding the sides of the band material that is to be wound or unwound on the core, the rear end flange 19 may be supplemented by a front end flange 30 which has an extension 31 that is insertable into the winding core. Radially movably mounted inside the winding mandrel 14 are three studs 20, each carrying a pin 22 for limiting the radial displaceability of the stud. The studs slide in slots in the winding mandrel 14. A peripheral recess 32 provided in the winding mandrel 14 in the same radial plane as the studs contains a thin elastic expandable ring 28. The outer surface of this ring should have the maximum possible coefficient of friction. The thickness of the ring is slightly less than the depth of the recess 32 to permit a winding core to be easily fitted and detached.

With reference to FIGS. 2a and 2b a radial bore in the winding mandrel 14 contains a pin 23 which serves as a stop cooperating with one of the rollers 13.

For firmly holding the winding core 29 the winding mandrel 14 is rotated clockwise from the position shown in FIG. 2a to that shown in FIG. 2b, causing the bevelled internal ends of the studs 20 to ride on to the rollers 13 which force them radially outwards against the inside of the elastic ring 28 thus causing the appertaining circumferential portion of this ring to be distorted or expanded in a radially outward direction so as to engage and grip with its outer frictionized surface the interior of the winding core 29 at three different places spaced apart. Since this rotation for gripping the core can be performed only by overcoming the friction between the brake disc 6 and the friction disc 18 the drive shaft 5 must either be braked or rotation must be by a rapid jerk, taking advantage of the inertia of the armature of the driving motor. The first of these two alternatives will be available if the transmission of the driving motor includes a self-locking gearing or a stop brake.

When the winding core 29 has been mounted and gripped by ring 28, the winding mandrel 14 is prevented from turning backwards and thereby from releasing the core by virtue of the friction between the brake disc 6 and the friction disc 18. This friction can be adjusted by means of the nut 25. The flange 19 which is attached to the winding mandrel 14 can be conveniently used for manually operating the mechanism. Owing to the relatively large diameter of the flange l9 and the resultant large leverage considerable gripping forces can be generated with little effort, and for the purpose of replacing a winding core the winding mandrel can be easily turned against the resistance of a fairly high coupling friction.

For releasing the winding core 29, the flange l9 and hence the mandrel 14 must be turned counter-clockwise from the position shown in FIG. 2b to that shown in FIG. 2a. This causes the studs 20 to ride off the rollers so that they can be pushed radially inwards by the elastic ring 28. The necessary rotation for effecting release (as when tightening) must again be accomplished by overcoming the friction between the brake disc 6 and the friction disc 18. The stop pin 23 limits the total angle of turn.

In order to prevent the winding core 29 from being accidentally released by a sudden jerk load, the direction in which the band tension principally acts is preferably arranged to generate a torque in the same direction as that required by shaft 5 for tightening the core on the mandrel 14.

The direction in which the band tension principally acts is indicated by an arrow A in FIGS. 2a and 2b. Jerks will then operate to pull the gripping device even tighter, instead of acting in the direction of releasing the core. If it is desired that the tensile pull should be in the opposite direction, as indicated by the arrow B, then the accidental release of winding core can still be prevented by turning the mandrel 60 in the clockwise direction. The rollers 13 can thus be made in a snap action to ride completely across the bevelled ends of the studs 20. This can be done only when no winding core has been mounted since the presence of a core would prevent the studs 20 from radially yielding sufficiently. According to the change in the main direction of tensile pull, the flange 19 must now be rotated counterclockwise for locating a winding core 19 and clockwise for releasing the same.

It is naturally within the scope of the present invention to provide only one or two or more than three studs for expanding the gripping ring 28. Particularly in the case of .wide winding cores it would also be feasible to provide two or more expandable friction rings side by side in order to distribute the gripping forces more evenly over the length of the core.

What is claimed is:

1. A core holding mechanism comprising;

a rotatable shaft,

a mandrel supporting thereon a cylindrical core and mounted coaxially with and rotatable relative to said shaft,

clutch means frictionally coupling said mandrel to said shaft,

actuating elements mounted on said shaft and rotatable therewith, and

gripping means radially mounted in said mandrel and engageable by said actuating elements upon rotation of the mandrel relative to the shaft against the force of said frictional clutch means to push the gripping means radially outwards and engage the inside surface of said core thereby holding the core firmly on the mandrel so that said core rotates with said shaft.

2. A mechanism according to claim 1 wherein said mandrel comprises a hollow cylinder, said cylinder being formed to provide a plurality of bores radially disposed about the axis of the cylinder, said gripping means comprises a plurality of studs each slidably mounted in a different one of said bores and said actuating elements comprise a plurality of rollers having their axes aligned with the axis of said shaft and positioned to engage said studs and push them radially outwards upon said relative rotation between the shaft and the mandrel.

3. A mechanism according to claim 1 wherein said clutch means comprises a friction disc mounted on one end of said mandrel and coaxial with said shaft and a braking disc secured to said shaft and in frictional contact with said friction disc.

4. A mechanism according to claim 3 including means for varying the frictional force provided by said clutch means, said frictional force varying means comprising a nut threaded on said shaft and spring means interposed between said nut and that end of said mandrel opposite said one end.

5. A mechanism according to claim 1 wherein said mandrel includes a manually operable flange for manually effecting said rotation of said mandrel relative to said shaft against the force of said frictional clutch means.

6. A mechanism according to claim 1 wherein said mandrel comprises a hollow cylinder, said cylinder being formed to provide three equiangularly spaced radial bores disposed about the axis of the cylinder and a peripherally extending recess into which said bores open, wherein said gripping means comprises a plurality of studs each slidably mounted in a different one of said bores and an elastically deformable ring seated in said recess, and wherein said actuating elements include a triangular plate secured fast to said shaft and rollers mounted respectively on said triangular plate at each of the three different apices thereof for rotation on an axis parallel to that of said shaft, each said roller being engageable with the radially inner end of a different one of said studs for efiecting radially outward displacement of said studs upon relative rotation as between said shaft and cylinder thereby to establish radially outward deformations of the corresponding peripheral portions of said elastic ring into a gripping contact with the inner surface of said core thereby to hold said core firmly on said mandrel. 

1. A core holding mechanism comprising; a rotatable shaft, a mandrel supporting thereon a cylindrical core and mounted coaxially with and rotatable relative to said shaft, clutch means frictionally coupling said mandrel to said shaft, actuating elements mounted on said shaft and rotatable therewith, and gripping means radially mounted in said mandrel and engageable by said actuating elements upon rotation of the mandrel relative to the shaft against the force of said frictional clutch means to push the gripping means radially outwards and engage the inside surface of said core thereby holding the core firmly on the mandrel so that said core rotates with said shaft.
 2. A mechanism according to claim 1 wherein said mandrel comprises a hollow cylinder, said cylinder being formed to provide a plurality of bores radially disposed about the axis of the cylinder, said gripping means comprises a plurality of studs each slidably mounted in a different one of said bores and said actuating elements comprise a plurality of rollers having their axes aligned with the axis of said shaft and positioned to engage said studs and push them radially outwards upon said relative rotation between the shaft and the mandrel.
 3. A mechanism according to claim 1 wherein said clutch means comprises a friction disc mounted on one end of said mandrel and coaxial with said shaft and a braking disc secured to said shaft and in frictional contact with said friction disc.
 4. A mechanism according to claim 3 including means for varying the frictional force provided by said clutch means, said frictional force varying means comprising a nut threaded on said shaft and spring means interposed between said nut and that end of said mandrel opposite said one end.
 5. A mechanism according to claim 1 wherein said mandrel includes a manually operable flange for manually effecting said rotation of said mandrel relative to said shaft against the force of said frictional clutch means.
 6. A mechanism according to claim 1 wherein said mandrel comprises a hollow cylinder, said cylinder being formed to provide three equiangularly spaced radial bores disposed about the axis of the cylinder and a peripherally extending recess into which said boRes open, wherein said gripping means comprises a plurality of studs each slidably mounted in a different one of said bores and an elastically deformable ring seated in said recess, and wherein said actuating elements include a triangular plate secured fast to said shaft and rollers mounted respectively on said triangular plate at each of the three different apices thereof for rotation on an axis parallel to that of said shaft, each said roller being engageable with the radially inner end of a different one of said studs for effecting radially outward displacement of said studs upon relative rotation as between said shaft and cylinder thereby to establish radially outward deformations of the corresponding peripheral portions of said elastic ring into a gripping contact with the inner surface of said core thereby to hold said core firmly on said mandrel. 